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Such a cure would entail transplanting differentiated embryonic stem cells derived from a cloned blastocyst, itself derived from the somatic nucleus of the patient's cell. This approach has attractive features. The chance of tissue rejection would be small, because the transplant would be derived from the patient. The proliferation of stem cells over a long period of time increases the odds that there will be enough cells for treatment. And the pluripotent nature of embryonic stem cells makes it possible to tailor the transplant according to the tissue type required.
The South Korean study is a step in a long journey. There are still many hurdles to clear before embryonic stem cells can be used therapeutically. For example, because undifferentiated embryonic stem cells can form tumors after transplantation in histocompatible animals, it is important to determine an appropriate stage of differentiation before transplantation. Differentiation protocols for many cell types have yet to be established. Targeting the differentiated cells to the appropriate organ and the appropriate part of the organ is also a challenge. Although these challenges are daunting, none are beyond theoretical reach.
Embryonic stem-cell lines are required to clear the hurdles between concept and practice. However, federal regulations limit their use because of the concern, as cited by President George W. Bush in 2001, that blastocysts "have at least the potential for life" and that therefore destroying them would cross "a fundamental moral line" (see http://whitehouse.gov/news/releases/2001/08/20010809-2.html). There are human embryonic stem-cell lines available for research involving the use of federal funds, but they are limited to lines established before 2001, when the "life and death decision" (as Bush put it) had already been made. At the moment, 15 such cell lines are available, and they are reportedly difficult to obtain, difficult to maintain, or poorly characterized.
It therefore comes as welcome news that a group led by Douglas Melton, a stem-cell researcher and father of children with type 1 diabetes, has derived, characterized, and prepared for dissemination 17 new human embryonic stem-cell lines. A description of the cell lines and their derivation is provided in the Special Report in this issue of the Journal.2 The report is notable in that it sets a standard for the characterization of embryonic stem-cell lines, and the cell lines described are easy to culture in vivo. Moreover, they are available to scientists with a Material Transfer Agreement, for noncommercial research purposes, albeit only those whose research on the cell lines will not make use of federal funds. It is not surprising that this resource comes from those in a position to recognize the therapeutic potential of stem-cell therapy.
These advances are the first steps in a path toward substantial progress in our ability to improve the health of patients, especially those with chronic debilitating diseases. In our opinion, the cell lines described by Melton and colleagues and the others that will follow should become part of the National Institutes of Health (NIH) Human Embryonic Stem Cell Registry (http://stemcells.nih.gov/registry/index.asp) for researchers funded by the NIH. There is too much suffering that may be remediable through the therapeutic application of this new approach to place the new cell lines off limits to many North American research scientists.
Source Information
This editorial was published at www.nejm.org on March 3, 2004.
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